The purchase of a modern computer-controlled X-ray diffractometer and computer with appropriate peripherals for rapidly collecting X-ray data and carrying out structure analyses is proposed. The instrument and computer would be used in the School of Chemical Sciences X-ray Service Laboratory to support the research of faculty, post-doctorates, and graduate students in biological chemistry and biochemistry at the University of Illinois. The determination of the structures of crystalline materials will be used to further greatly research in the following areas: the biosynthesis of isoprenoid natural products; the synthesis of antibiotics in the mitomycin class; probing the role of transition metal ions in biological electron transfer mechanisms; synthetic and physical studies of anticancer agents; the determination of transition state geometry relevant to phosphate ester hydrolysis, the determination of the structures of natural products from marine sources; the determination of the structures of antibiotics and antifungal agents; the investigation of the three-dimensional structures of the enzymes, pyruvate oxidase and chloroperoxidase, and of the troponin complex involved in muscle contraction. The proposed X-ray equipment would greatly improve the capability of the School X-ray Service to provide a structural service on a very fast time frame (approximately 1 week) and allow investigations to be made on protein structures.